getDeclaredFields()应用

调用private类型的变量及方法

BeanUtils.java

package com.lmb.util;import org.apache.commons.lang.StringUtils;import org.apache.commons.logging.Log;import org.apache.commons.logging.LogFactory;import org.springframework.util.Assert;import org.springframework.util.ReflectionUtils;import java.lang.reflect.Field;import java.lang.reflect.Method;import java.util.ArrayList;import java.util.List;/** * 扩展Apache Commons BeanUtils, 提供一些反射方面缺失功能的封装. */public class BeanUtils extends org.apache.commons.beanutils.BeanUtils {    protected static final Log logger = LogFactory.getLog(BeanUtils.class);    private BeanUtils() {    }    /**     * 循环向上转型,获取对象的DeclaredField.     *     * @throws NoSuchFieldException 如果没有该Field时抛出.     */    public static Field getDeclaredField(Object object, String propertyName) throws NoSuchFieldException {        Assert.notNull(object);        Assert.hasText(propertyName);        return getDeclaredField(object.getClass(), propertyName);    }    /**     * 循环向上转型,获取对象的DeclaredField.     *     * @throws NoSuchFieldException 如果没有该Field时抛出.     */    public static Field getDeclaredField(Class clazz, String propertyName) throws NoSuchFieldException {        Assert.notNull(clazz);        Assert.hasText(propertyName);        for (Class superClass = clazz; superClass != Object.class; superClass = superClass.getSuperclass()) {            try {                return superClass.getDeclaredField(propertyName);            } catch (NoSuchFieldException e) {                // Field不在当前类定义,继续向上转型             }        }        throw new NoSuchFieldException("No such field: " + clazz.getName() + '.' + propertyName);    }    /**     * 暴力获取对象变量值,忽略private,protected修饰符的限制.     *     * @throws NoSuchFieldException 如果没有该Field时抛出.     */    public static Object forceGetProperty(Object object, String propertyName) throws NoSuchFieldException {        Assert.notNull(object);        Assert.hasText(propertyName);        Field field = getDeclaredField(object, propertyName);        boolean accessible = field.isAccessible();        field.setAccessible(true);        Object result = null;        try {            result = field.get(object);        } catch (IllegalAccessException e) {            logger.info("error wont' happen");        }        field.setAccessible(accessible);        return result;    }    /**     * 暴力设置对象变量值,忽略private,protected修饰符的限制.     *     * @throws NoSuchFieldException 如果没有该Field时抛出.     */    public static void forceSetProperty(Object object, String propertyName, Object newValue)            throws NoSuchFieldException {        Assert.notNull(object);        Assert.hasText(propertyName);        Field field = getDeclaredField(object, propertyName);        boolean accessible = field.isAccessible();        field.setAccessible(true);        try {            field.set(object, newValue);        } catch (IllegalAccessException e) {            logger.info("Error won't happen");        }        field.setAccessible(accessible);    }    /**     * 暴力调用对象函数,忽略private,protected修饰符的限制.     *     * @throws NoSuchMethodException 如果没有该Method时抛出.     */    @SuppressWarnings("unchecked")    public static Object invokePrivateMethod(Object object, String methodName, Object... params)            throws NoSuchMethodException {        Assert.notNull(object);//object对象不为空，否则抛出异常        Assert.hasText(methodName);//methodName 不能为 null 且必须至少包含一个非空格的字符，否则抛出异常        Class[] types = new Class[params.length];        for (int i = 0; i < params.length; i++) {            types[i] = params[i].getClass();        }        Class clazz = object.getClass();        Method method = null;        for (Class superClass = clazz; superClass != Object.class; superClass = superClass.getSuperclass()) {            try {                //获取superClass类自身声明的符合入参要求的所有方法，包含public、protected和private方法                method = superClass.getDeclaredMethod(methodName, types);                break;            } catch (NoSuchMethodException e) {                // 方法不在当前类定义,继续向上转型            }        }        if (method == null)            throw new NoSuchMethodException("No Such Method:" + clazz.getSimpleName() + methodName);        boolean accessible = method.isAccessible();//获取方法的可用性情况        method.setAccessible(true);        Object result = null;        try {            result = method.invoke(object, params);//调用该方法        } catch (Exception e) {            ReflectionUtils.handleReflectionException(e);        }        method.setAccessible(accessible);//还原方法的可用性情况        return result;    }    /**     * 按Filed的类型取得Field列表.     */    public static List<Field> getFieldsByType(Object object, Class type) {        List<Field> list = new ArrayList<Field>();        Field[] fields = object.getClass().getDeclaredFields();        for (Field field : fields) {            if (field.getType().isAssignableFrom(type)) {                list.add(field);            }        }        return list;    }    /**     * 按FiledName获得Field的类型.     */    public static Class getPropertyType(Class type, String name) throws NoSuchFieldException {        return getDeclaredField(type, name).getType();    }    /**     * 获得field的getter函数名称.     */    public static String getGetterName(Class type, String fieldName) {        Assert.notNull(type, "Type required");        Assert.hasText(fieldName, "FieldName required");        if (type.getName().equals("boolean")) {            return "is" + StringUtils.capitalize(fieldName);        } else {            return "get" + StringUtils.capitalize(fieldName);        }    }    /**     * 获得field的getter函数,如果找不到该方法,返回null.     */    public static Method getGetterMethod(Class type, String fieldName) {        try {            return type.getMethod(getGetterName(type, fieldName));        } catch (NoSuchMethodException e) {            logger.error(e.getMessage(), e);        }        return null;    }}

实现java反射调用别的类

写一个类Simple.java

public class Simple { private void displayMessage(String strMsg) {  System.out.println("message is:" + strMsg); }}

反射调用

import java.lang.reflect.*;public class Test { /**  * @param args  * @throws ClassNotFoundException  * @throws NoSuchMethodException  * @throws SecurityException  * @throws IllegalAccessException  * @throws InstantiationException  * @throws InvocationTargetException  * @throws IllegalArgumentException  */ public static void main(String[] args) throws ClassNotFoundException,   SecurityException, NoSuchMethodException, InstantiationException,   IllegalAccessException, IllegalArgumentException,   InvocationTargetException {  Class simpleClass = Class.forName("Simple");  Object simpelObject = simpleClass.newInstance();//获取simple类的实例对象  Class[] args1 = new Class[1];  args1[0] = String.class;  Method simpleMethod = simpleClass.getDeclaredMethod("displayMessage",    args1);//得到方法名为displayMessage，参数类型为args1内的参数类型的方法（private public protected）  simpleMethod.setAccessible(true);//设置方法可用  String[] argments = new String[1];  argments[0] = "Hello,world";  simpleMethod.invoke(simpelObject, argments);//调用该方法 }}